Synthesis Of Dimethyldichlorosilane By Catalytic Disproportionation Of Methyltrichlorosilane Over Modified MCM-41

In recent years, the organosilicon industry develops rapidly. As is known, the organosilicon monomers are the fundamental of the production of silicone materials. One of the most important is methylchlorosilanes which are widely applied in the organosilicon industry, among these methylchlorosilanes,(CH3)2SiCl2(DMCS) is the most valuable which is produced by using the Rochow direct process. However, Rochow direct process prepare not only the main product DMCS but also many by-products, especially methyltrichlorosilane (MTS) whose content is5-15%of the total product. About500,000tons of MTS have been produced each year worldwide at present. And disproportionation of MTS and redistribution of MTS with methyl-rich chlorosilane to produce dimethyldichlorosilane are promising ways to consume the bulk of MTS, which can not only solve the accumulated problem of MTS in DMCS producing process, but also achieve the resources’ cycling.In this master thesis, Al-MCM-41and Ce-Al-MCM-41which were modified by inserting aluminium and Ce into the lattice of MCM-41were using as catalysts. And incorporation of the heteroatoms enhanced the acidity of MCM-41. The influences of the acid type and amount of acid on the reaction were also studied. The catalysts were characterized by FT-IR, X-ray powder diffraction (XRD),27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and N2absorption-desorption. It reveals that there are some difference in the apparent physical propertie and amount of acid by the addition of aluminium (or Ce). With the incensement of the content of aluminium (or Ce), the BET surface area showed a slight decrease. However all samples show the hexagonal structure of MCM-41and exhibit large BET surface areas which are also over842m2?g-1(769m2?g-1). And FT-IR spectra of pyridine adsorption was also used to stdudy the acidic of Al-MCM-41(or Ce-Al-MCM-41), the results demonstrates that Al-MCM-41(or Ce-Al-MCM-41) samples have Lewis (L) and Br(?)nsted (B) acidic sites, and the amount of acidic sites can be modulated by the incorporation of aluminium (or Ce). Besides the B acidic sites are stable in the temperature ranging from423to623K.Al-MCM-41and Ce-Al-MCM-41catalysts were applied to disproportionate MTS to prepare DMCS under atmospheric pressure. The effects of Si/Al, Al/Ce and temperature on the disproportionation reaction were also investigated. The activity results show that when the Si/Al is15:1, Al-MCM-41exhibits an excellent activity with100%conversion of MTS and47%selectivity of DMCS at623K under atmospheric pressure. It is also found that the presence of L acidic site can improve the DMCS yield when the B acidic site is stable. When Ce is inserted in the Al-MCM-41, the activity can be improved; when Al/Ce is2:1, Ce-Al-MCM-41exhibits an excellent activity with100%conversion of MTS and50%selectivity and yield of DMCS at623K under atmospheric pressure. The resistance to coking of the catalyst can be enhanced because of the present of Ce.